The present invention disclosed herein relates to an apparatus for treating a substrate, and more particularly, to a rotatable spin head configured to support a substrate, for example, in a semiconductor process, and a method for treating a substrate using the spin head.
Semiconductor processes include a process of etching or cleaning thin layers, foreign substances, and particles. Such an etching or cleaning process may be performed by placing a substrate such as a wafer on a spin head with a patterned side of the wafer facing upward or downward and supplying a process liquid to the wafer while rotating the spin head. The spin head includes chuck pins to support the edge of the wafer for preventing the wafer from being detached from the spin head in a radial direction. The chuck pins can be moved between rest positions and supporting positions. When the chuck pins are in the rest positions, a loading/unloading space is formed on the spin head for loading and unloading a substrate. When a substrate loaded on the spin head is treated while rotating the spin head, the chuck pins are in supporting positions where the chuck pins make contact with the edge of the substrate and support the substrate.
FIG. 23 illustrates a typical spin head 900. The spin head 900 includes a rotatable body 920, support pins 960 configured to support a bottom surface of a substrate (W), and chuck pins 940 configured to support the edge of the substrate (W). Each of the chuck pins 940 includes a rotatable vertical rod 942 and a support rod 944 protruding upward from the vertical rod 942. The support rod 944 and the vertical rod 942 are eccentric. A process liquid is supplied to a front center portion of the substrate (W), and gas is supplied to the bottom surface of the substrate (W) to prevent the process liquid from reaching a predetermined region of the bottom surface of the substrate (W).
FIG. 24 is a top view for explaining disadvantages of chuck pins such as the chuck pins 940 of FIG. 23. The vertical rods 942 are disposed close to the substrate (W), and the support rods 944 have a circular shape. Therefore, when the substrate (W) is rotated, streams flowing from the front center portion of the substrate (W) are largely separated at the support rods 944. That is, a process liquid is not smoothly supplied to regions of the substrate (W) close to the support rods 944.
FIG. 25 is a bottom view of the substrate (W) for explaining disadvantages of support pins such as the support pins 960 of FIG. 23. In the case where the support pins 960 are disposed between the substrate (W) and the rotatable body 920 as shown in FIG. 23, streams of gas supplied to a bottom surface of the substrate (W) are separated at the support pins 960. Therefore, gas is not sufficiently supplied to regions of the bottom surface of the substrate (W) close to the support pins 960, and thus a process liquid can permeate between the substrate (W) and the rotatable body 920 past the support pins 960. As a result, an edge portion of the bottom surface of the substrate (W) may be non-uniformly treated. In addition, since the vertical rods 942 of the chuck pins 940 impede streams of gas supplied to the bottom surface of the substrate (W), a process liquid can permeate between the substrate (W) and the rotatable body 920 past the vertical rods 942.
In general, the support rods 944 are moved together from rest positions to supporting positions by a single driving mechanism. Therefore, if the support rods 944 are not uniform in size due to machining tolerances, some of the support rods 944 may not be brought into contact with the edge of the substrate (W) although all the support rods 944 are moved together to the supporting positions. Thus, the substrate (W) may be unstably supported, and the other chuck pins making contact with the edge of the substrate (W) may be easily damaged due to concentration of stress.
In addition, if the spin head 900 is rotated at high speed, since a strong centrifugal force is applied to the support rods 944 in a direction from the supporting positions to the rest positions, the substrate (W) may be unstably supported.